Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$152.49	10.254%	$168.1263	$168.13	$168.15	$168.10
Purchase #2	$179.83	10.527%	$198.7607	$198.76	$198.75	$198.80
Purchase #3	$154.28	9.622%	$169.1248	$169.12	$169.10	$169.10
Purchase #4	$102.81	12.584%	$115.7476	$115.75	$115.75	$115.70
Purchase #5	$179.57	8.171%	$194.2427	$194.24	$194.25	$194.20
Purchase #6	$174.37	6.106%	$185.017	$185.02	$185.00	$185.00
Purchase #7	$146.95	12.633%	$165.5142	$165.51	$165.50	$165.50
7 purchase totals =	$1,090.30		$1,196.5333	$1,196.53	$1,196.50	$1,196.40